caseActivityDefinitionId - a String value. This is the same as CaseActivityDefinition.getDefinitionId

payload - a Map value. This information is optional. For case activities that map case data to data initiating case activity, this is not needed. When there are case activities which require use to provide data for initiation, this data is required. For initiating activities that are implemented using BPMN or Human Task, the type of Object is expected to be an XML Node